This invention relates to the field of electro-optical detecting apparatus which utilizes "mosaic" detector arrays to provide surveillance of an extensive scene. The mosaic detector arrays are large numbers of closely spaced individual photodetector elements (either photo-conductors or photo-diodes) arranged in essentially a two-dimensional, or planar, array.
An overall system incorporating such mosaic detector arrays is disclosed in U.S. Pat. Nos. 3,852,714 and 3,970,990, based on the inventions of John C. Carson, one of the joint applicants herein. Those patents provide a full explanation of the reasons for, and benefits of, such detector arrays and the adaptive imaging systems in which they are incorporated.
In FIGS. 6 and 16 of each of the Carson patents, specific mosaic detector array modules are disclosed. The present invention is concerned both with improving the structures of such detector array modules, and with providing a more practical method of fabricating such structures.
It is very important to provide a module wherein the electrical conductors and electronic chips associated with the detectors are housed in the "volume" of space created by extending the two-dimensional surface area of the detector array in a direction perpendicular to that two-dimensional surface. This permits large numbers of such modules to be located contiguously, so that a continuous detector-filled surface is provided. In other words, the dimension perpendicular to the plane of the detectors is used to package the conductor leads connected to the detectors, and also electronics associated with individual detectors or groups of detectors.
Another crucial consideration is the fabrication method used in constructing the modules. A problem encountered with the module structures and fabrication methods disclosed in the Carson patents is the difficulty of providing accurate alignment of the conductors which are located in separate layers of the module. The alignment requirements are extremely hard to satisfy because of the need to connect the conductors separately to the multiplicity of very closely spaced detector elements.
Another problem encountered is the current inadequacy of the state of the art relating to metallized holes, or vias, which were relied on as conductors in the modules disclosed in the Carson patents. Two module designs are shown in those patents, one in FIG. 6 and one in FIG. 16, both of which use vias as part of the electrical conductor pattern.